Fix warning

Author: samedson

Crashlytics/UnitTests/FIRCrashlyticsReportTests.m

@@ -235,10 +235,10 @@ - (void)testLogLimits {
     [report log:@"0123456789"];
   }
 
-  NSUInteger sizeA = [[[NSFileManager defaultManager]
+  unsigned long long sizeA = [[[NSFileManager defaultManager]
       attributesOfItemAtPath:[report.internalReport pathForContentFile:FIRCLSReportLogAFile]
                        error:nil] fileSize];
-  NSUInteger sizeB = [[[NSFileManager defaultManager]
+  unsigned long long sizeB = [[[NSFileManager defaultManager]
       attributesOfItemAtPath:[report.internalReport pathForContentFile:FIRCLSReportLogBFile]
                        error:nil] fileSize];